EP2842716A1 - Worm machine and method for the treatment of plastic melts - Google Patents

Abstract

A screw machine has for preparing a plastic melt (38) a housing (2) with at least one housing bore (15) formed therein, in which at least one treatment element shaft (17) is arranged and is rotatably driven about an associated axis of rotation (19). For the treatment of the plastic melt (38), the at least one treatment element shaft (17) has a plurality of treatment elements (29 ', 30') which are rotationally fixed in succession on at least one associated shaft (28) in a conveying direction (3) of the plastic melt (38) , For supporting the at least one shaft (28) in the housing (2), at least one shaft bearing (48) is arranged upstream of a feed opening (45) relative to the conveying direction (3). The at least one shaft bearing (48) is hydrodynamically formed. As a result, a shaft bearing with less wear compared to the prior art is possible in a simple manner.

Description

The invention relates to a screw machine for the treatment of plastic melts according to the preamble of claim 1. Furthermore, the invention relates to a method for the treatment of plastic melts.

From the EP 2 082 862 A1 a worm machine is known, whose shafts are cantilevered at an upstream end of the housing by means of plain bearings and sealed by means of a cloth liner. The sliding bearing consists of a sintered metal, in particular of sintered bronze. The disadvantage is that the storage of the waves is complex and yet subject to wear, so that the storage must be maintained at regular intervals.

The invention has for its object to provide a screw machine for the treatment of plastic melts, which allows a simple way a shaft bearing with relatively less wear.

This object is achieved by a screw machine with the features of claim 1. The at least one shaft bearing upstream of the feed opening is formed hydrodynamically according to the invention, whereby a contact-free and thus wear-free storage is achieved in a simple manner. In particular, in the shaft bearing can be dispensed with quality materials or material pairings, whereby the shaft bearing is easier and less expensive. The hydrodynamic design of the at least one shaft bearing takes place in particular by means of the plastic melt to be processed. As a result, the plastic melt to be processed is used at the same time for shaft bearing in a simple manner.

The worm machine is designed in particular as a multi-shaft worm machine, preferably as a twin-shaft worm machine. The treatment element waves of the multi-shaft screw machine or twin-shaft screw machine are in particular in the same direction rotatably drivable and formed dichtkämmend.

A screw machine according to claim 2 ensures a non-contact and wear-free shaft bearing. As soon as the at least one shaft is rotationally driven, a sliding film or lubricating film forms in the respective bearing gap, ie between the at least one shaft and the housing. The sliding film is formed substantially symmetrically or rotationally symmetric due to a - normally - symmetrical pressure distribution. When radial loads act on the at least one shaft, it shifts radially, creating an asymmetric sliding film and an asymmetric pressure distribution that compensate for the radial loads. The bearing gap is preferably charged with the plastic melt to be processed.

A screw machine according to claim 3 ensures a simple and reliable shaft bearing. The gap width B ensures that the sliding film on the one hand has a sufficient radial thickness to compensate for radial loads, and on the other hand that the radial thickness of the sliding film is not too large to allow a stable shaft bearing.

A screw machine according to claim 4 ensures a simple and reliable shaft bearing. The gap length L ensures that the bearing gap on the one hand in the axial direction is sufficiently long to distribute the occurring radial loads over the gap length and compensate in conjunction with the gap width, and that the gap length on the other hand is not too long to a large flow resistance to avoid and to ensure a reliable lubrication.

A screw machine according to claim 5 allows a simple way hydrodynamic shaft bearing. Due to the fact that the respective bearing gap is flowed through by the plastic melt to be processed, the plastic melt simultaneously forms the sliding film or lubricating film in a simple manner. Preferably, the plastic melt to be processed is divided into a main flow and a secondary flow, wherein the bearing gap is flowed through by the secondary flow. Preferably, the bearing gap with the at least one housing bore in connection, so that either the plastic melt or the secondary flow to the bearing gap from the at least one housing bore can be fed and / or the plastic melt or the secondary stream after flowing through the bearing gap in the at least one housing bore can be discharged is. As a result, a simple supply and / or discharge of the plastic melt or the secondary flow is ensured.

A screw machine according to claim 6 ensures a simple shaft bearing. The secondary flow of the plastic melt is supplied to the main flow after flowing through the bearing gap, so that the plastic melt used for the hydrodynamic shaft bearing is further processed. Disposal of the hydrodynamic Storage used plastic melt is eliminated by this. In addition, the entire plastic melt is retained in the treatment process.

A screw machine according to claim 7 ensures in a simple manner the supply of the plastic melt to the respective bearing gap. The plastic melt supplied to the screw machine is divided in the at least one housing bore into a main flow and a secondary flow. The secondary flow flows through against the conveying direction of the main flow to the respective bearing gap. For this purpose, the plastic melt is supplied, for example, with a correspondingly high melt pressure in the at least one housing bore, so that the main flow is conveyed in the usual manner in the conveying direction and the secondary flow is forced through the respective melt channel. In addition, for example, a feed element can be arranged in the feed section, which conveys the secondary flow counter to the conveying direction of the main flow to the respective bearing gap. After flowing through the bearing gap, the secondary flow can be returned to the main flow. For this purpose, the respective melt channel opens again into the feed opening or into the at least one housing bore. The melt channel can be formed in sections in the housing and / or outside the housing or externally for returning the secondary flow.

A screw machine according to claim 8 ensures a reliable shaft bearing. The charging element ensures in a simple manner a supply of the associated storage gap with the plastic melt to be processed. The supply is in particular independent of the melt pressure with which the plastic melt is supplied. A screw machine according to claim 9 ensures a simple hydrodynamic shaft bearing. The plastic melt is divided before being fed into the at least one housing bore into a main flow and a secondary flow. The main stream is fed to the preparation in the at least one housing bore. The secondary flow is guided in the conveying direction of the main flow through the respective bearing gap. Preferably, the secondary flow is then guided into the at least one housing bore. Due to a sufficiently high melt pressure, the secondary flow is preferably forced through the respective melt channel or the respective bearing gap.

A screw machine according to claim 10 ensures a possible wear-free startup of the screw machine. By means of the starting pump, the at least one shaft bearing or the associated bearing gap is prefilled with a lubricant prior to starting the screw machine. The lubricant may for example be a grease and / or the plastic melt. The start-up takes place in particular at reduced load, so that the starting takes place as wear-free as possible. Alternatively or additionally, for the initial start-up of the screw machine in the at least one bearing gap plastic molded body can be inserted, such as plastic strips, which melt at the first start in the at least one bearing gap and minimize wear during startup.

A screw machine according to claim 11 ensures in a simple manner a reliable shaft bearing. Due to the temperature controllability of the housing and / or the at least one shaft, the hydrodynamic bearing properties of the at least one shaft bearing can be influenced as required. For example, when flowing through the Storage gap high heat generation due to a high viscosity of the plastic melt, so the at least one shaft bearing or the bearing can be cooled. The housing and / or the at least one shaft is formed in particular coolable in the region of the at least one shaft bearing.

A screw machine according to claim 12 ensures a simple sealing of the at least one shaft. The sealing element is designed in particular as a non-contact sealing element and thus maintenance-free, for example as a threaded shaft sealing element. By means of the threaded shaft sealing element, the plastic melt or the secondary flow is conveyed in the direction of the at least one housing bore and constructed accordingly for sealing a back pressure. The plastic melt or the secondary stream is preferably conveyed back into the melt channel and / or the at least one housing bore.

The invention is further based on the object to provide a method for the preparation of plastic melts, which allows a simple way a shaft bearing with relatively less wear.

This object is achieved by a method having the features of claim 13. The advantages of the method according to the invention correspond to the already described advantages of the screw machine according to the invention, to which reference is hereby made. The method can be developed in particular with the features of claims 2 to 12.

A method according to claim 14 ensures a simple and reliable hydrodynamic shaft bearing. Because of the plastic melt is divided into a main flow and a secondary flow, only the secondary flow must be passed through the respective bearing gap of the at least one shaft bearing for hydrodynamic bearing of at least one shaft. The secondary flow thus ensures a simple way a wear-free shaft bearing. At the same time, the throughput of the screw machine is not affected because the main stream does not have to flow through the bearing gap. Preferably, the secondary stream is fed back to the main stream after flowing through the storage gap, so that disposal of plastic melt is eliminated and the entire plastic melt is processed.

A method according to claim 15 ensures a reliable hydrodynamic shaft bearing. The melt pressure ensures that the plastic melt or the secondary stream flows through the respective bearing gap continuously, ie without interruption. The melt pressure can be provided, for example, by means of a melt pump. The melt pressure is preferably adjustable as needed or plastic melt. The melt pressure indicates the pressure of the plastic melt minus the ambient pressure.

Fig. 1

eine teilweise geschnitten dargestellte Mehrwellen-Schneckenmaschine gemäß einem ersten Ausführungsbeispiel mit hydrodynamisch gelagerten Wellen,

Fig. 2

eine teilweise geschnittene Draufsicht auf die Mehrwellen-Schneckenmaschine in Fig. 1,

Fig. 3

einen Querschnitt durch die Mehrwellen-Schneckenmaschine entlang der Schnittlinie III-III in Fig. 2,

Fig. 4

eine vergrößerte Darstellung der Mehrwellen-Schnecken-maschine im Bereich der hydrodynamisch gelagerten Wellen,

Fig. 5

einen Querschnitt durch die Mehrwellen-Schneckenmaschine entlang der Schnittlinie V-V in Fig. 4, und

Fig. 6

eine vergrößerte und teilweise geschnittene Darstellung einer Mehrwellen-Schneckenmaschine gemäß einem zweiten Ausführungsbeispiel mit hydrodynamisch gelagerten Wellen.

Further features, advantages and details of the invention will become apparent from the following description of several embodiments. Show it:

Fig. 1

a partially cut illustrated multi-shaft screw machine according to a first embodiment with hydrodynamically mounted shafts,

Fig. 2

a partially sectioned plan view of the multi-shaft screw machine in Fig. 1 .

Fig. 3

a cross section through the multi-shaft screw machine along the section line III-III in Fig. 2 .

Fig. 4

an enlarged view of the multi-shaft screw machine in the area of hydrodynamically mounted shafts,

Fig. 5

a cross section through the multi-shaft worm machine along the section line VV in Fig. 4 , and

Fig. 6

an enlarged and partially sectioned view of a multi-shaft screw machine according to a second embodiment with hydrodynamically mounted shafts.

The following is based on the Fig. 1 to 5 a first embodiment of the invention described. A multi-shaft screw machine 1 has a housing 2 made up of a plurality of housing sections 4 to 13 arranged one after the other in a conveying direction 3 and designated as housing sections. The housing sections 4 to 13 are connected to each other via flanges, not shown, and form the housing 2.

In the housing sections 5 to 13 two mutually parallel and interpenetrating housing bores 14, 15 are formed, which have the shape of a horizontal eight in cross section. In the housing bores 14, 15 concentrically two treatment element shafts 16, 17 are arranged, which are rotatably driven about associated axes of rotation 18, 19.

The screw machine 1 has in succession in the conveying direction 3 a feed zone 20, a first treatment zone 21, a degassing zone 22, a second treatment zone 23 and a pressure buildup zone 24. The housing 2 is closed off at the last housing section 13 by an adapter plate 25, which has a discharge opening 26.

The treatment element shafts 16, 17 are formed by shafts 27, 28 with treatment elements 29 to 37 or 29 'to 37' arranged thereon. The treatment elements 29 to 37 arranged on the first shaft 27 and the treatment elements 29 'to 37' arranged on the second shaft 28 correspond to each other, the reference numerals of the treatment elements 29 'to 37' arranged on the second shaft 28 being distinguished by a "'". exhibit. In the feed zone 20, the degassing zone 22 and the pressure buildup zone 24, the treatment elements 29, 29 ', 30, 30', 33, 33 ', 36, 36' and 37, 37 'are formed as screw elements, whereas the treatment elements 31, 31' , 32, 32 ', 34, 34' and 35, 35 'are formed in the processing zones 21 and 23 as kneading elements. The treatment elements 29 to 37 or 29 'to 37' are designed to treat or treat a plastic melt 38 in pairs tightly combing. For degassing the plastic melt 38, the housing section 9 has a degassing opening 39.

The treatment element shafts 16, 17 are by means of a drive motor 40 and an associated branching gear 41 in the same direction, ie in the same directions of rotation 42, 43 about the axes of rotation 18, 19 rotatably driven. Between the drive motor 40 and the branching gear 41, a clutch 44 is arranged.

For the rotationally fixed arrangement of the treatment elements 29 to 37 or 29 'to 37', the shafts 27, 28 are provided in the region of the treatment elements 29 to 37 or 29 'to 37' with an outer profile A, which with a respective inner profile I of the treatment elements 29 to 37 or 29 'to 37' generates the rotationally fixed connection.

For supplying the plastic melt 38, a feed opening 45 is formed in the housing section 5, which opens into the housing bores 14, 15. The plastic melt 38 can be fed, for example, by means of a melt pump with an adjustable melt pressure p through the feed opening 45 into the housing bores 14, 15.

For supporting the shafts 27, 28, the screw machine 1 has two shaft bearings 47, 48 upstream of the housing section 4, relative to the conveying direction 3. The shaft bearings 47, 48 are hydrodynamically formed and are also referred to below as hydrodynamic shaft bearings 47, 48.

To form the hydrodynamic shaft bearings 47, 48, two bearing bores 49, 50 are formed in the housing section 4. The bearing bores 49, 50 extend from the housing bores 14, 15 concentrically to the axes of rotation 18, 19 through the housing section 4 to the branching gear 41. The bearing bores 49, 50 have a diameter D _L , which is smaller than a diameter D _G. the housing bores 14, 15, so that the bearing bores 49, 50 do not intersect.

The shafts 27, 28 are guided by the associated bearing bores 49, 50. To form the hydrodynamic shaft bearings 47, 48 point the shafts 27, 28 associated bearing portions 51, 52 which form a first smooth bearing surface L ₁ . Correspondingly, the bearing bores 49, 50 have second smooth bearing surfaces L ₂ in the region of the bearing sections 51, 52. The bearing bores 49, 50 and the associated bearing sections 51, 52 define associated bearing gaps 53, 54 with their bearing surfaces L ₁ and L _2. The shafts 27, 28 have a diameter D _W in the area of the bearing sections 51, 52 which is smaller than the diameter Diameter D _L is, so that the bearing gaps 53, 54 in the concentric arrangement of the shafts 27, 28 in the bearing bores 49, 50 are annular and over the entire circumference have a radial gap width B. For the ratio of the gap width B to the diameter D _W : 0.0005 ≦ B / D _W ≦ 0.02, in particular 0.001 ≦ B / D _W ≦ 0.01, and in particular 0.002 ≦ B / D _W ≦ 0.005.

The bearing gaps 53, 54 furthermore have a gap length L in the direction of the axes of rotation 18, 19. For the ratio of the gap length L to the diameter D _W : 0.25 ≦ L / D _W ≦ 6, in particular 0.5 ≦ L / D _W ≦ 4, and in particular 1 ≦ L / D _W ≦ 2

To form the hydrodynamic shaft bearings 47, 48, the bearing gaps 53, 54 can be flowed through by the plastic melt 38. For this purpose, the screw machine 1 has melt channels 55, 56 which, as the respective section, comprise the bearing gap 53 or 54. Fig. 4 shows the melt channel 56 with the associated bearing gap 54.

The melt channels 55, 56 are identical, so that only the melt channel 56 is described below. The melt channel 56 comprises, starting from the housing bore 15, a feed section 57, the bearing section 52, a discharge section 58 and a return section 59. The feed section 57 extends from the feed opening 45 to the bearing gap 54. In the feed section 57, a feed element 60 designed as a screw element is arranged on the shaft 28. The feed element 60 has a feed conveying direction 61, which is directed opposite to the conveying direction 3. The charging element 60 is rotatably mounted on the shaft 28 corresponding to the treatment elements 29 'to 37'. Relative to the conveying direction 3, the feed section 57 is thus arranged downstream of the respectively associated bearing gap 53, 54.

The discharge section 58 is arranged downstream of the bearing gap 54 in the feed conveying direction 61. In the discharge section 58, the shaft 28 has a diameter D _A , which is smaller than the diameter D _L , so that in the discharge section 58 between the shaft 28 and the housing portion 4 in the bearing bore 50, a comparatively large annular space is formed in the the plastic melt 38 can be discharged from the bearing gap 54. The plastic melt 38 can be returned to the feed opening 45 via the return section 59. The return section 59 is formed in sections as a channel in the housing section 4 and arranged as outside the housing section 4 return line. The same applies to the melt channel 55 and the associated bearing gap 53.

The housing portion 4 is formed in the region of the shaft bearings 47, 48 tempered. For this purpose, a plurality of temperature control channels 62 are formed in the housing section 4, into which a temperature control means 63 can be fed. Preferably, the temperature control channels 62 and the temperature control 63 serve for cooling. Furthermore, the shafts 27, 28 in the region of the shaft bearings 47, 48 formed tempered. For this purpose, in the waves 27, 28 tempering 67 formed, which can be filled with a temperature control 68 or flowed through by this. Preferably, the temperature control channels 67 and the temperature control 68 serve for cooling.

In the conveying direction 3 upstream of the shaft bearings 47, 48 and in the feed conveying direction 61 downstream, a non-contact sealing element 64 is arranged in each case. The sealing elements 64 are designed as threaded shaft sealing elements. The threaded shaft sealing elements 64 are rotatably mounted on the shafts 27 and 28 in the manner already described. The threaded shaft sealing elements 64 have a conveying direction which corresponds to the conveying direction 3. The threaded shaft sealing elements 64 are arranged in the feed conveying direction 61 downstream of the discharge section 58, so that the plastic melt 38 can be introduced into the return section 59.

To start the screw machine 1, a start pump 46 is provided, which serves for supplying a lubricant, in particular the plastic melt 38 to the shaft bearings 47, 48. The starting pump 46 can be connected to the melt channels 55, 56, so that before starting the screw machine 1, the lubricant or plastic melt 38 can be conveyed into the bearing gaps 53, 54. The starting pump 46 is in Fig. 4 indicated.

The operation of the screw machine 1 is described below:

To start the screw machine, the starting pump 46 is first connected to the melt channels 55, 56. Subsequently, plastic melt 38 is conveyed into the bearing gaps 53, 54 by means of the starting pump 46.

If the bearing gaps 53, 54 filled with plastic melt 38, the starting pump 46 is again separated from the melt channels 55, 56.

Subsequently, the plastic melt 38 is supplied with a melt pressure p through the feed opening 45 in the housing bores 14, 15 and the screw machine 1 approached. For the melt pressure p, which designates the differential pressure between the pressure of the plastic melt 38 and the ambient pressure, the following applies: 0.01 bar ≦ p ≦ 20 bar, in particular 0.1 ≦ p ≦ 10 bar, in particular 0.5 bar ≦ p ≦ 5 bar, and in particular 1 bar ≤ p ≤ 3 bar.

In the housing bores 14, 15, the plastic melt 38 is divided into a main flow and a secondary flow. In Fig. 4 the main flow is indicated by arrows marked H, whereas the side flow is indicated by arrows labeled N. The main stream H is conveyed in the usual way by means of the treatment elements 29 to 37 and 29 'to 37' in the conveying direction 3 and the plastic melt 38 is processed in the usual way. In contrast, the secondary flow N is conveyed to the hydrodynamic shaft bearings 47, 48 by means of the feed elements 60 in the feed direction 61, ie opposite to the conveying direction 3. The plastic melt 38 flows through the bearing gaps 53, 54, whereby the shafts 27, 28 are mounted hydrodynamically in the region of the bearing sections 51, 52. The plastic melt 38 forms a sliding film or lubricating film in the bearing gaps 53, 54. Due to the rotation of the shafts 27, 28, the pressure distribution in the bearing gaps 53, 54 is substantially symmetrical, so that the sliding film forms symmetrically or rotationally symmetrically. Acting radial loads on the shafts 27, 28, so they shift in the bearing bores 49, 50, resulting in an asymmetric pressure distribution and forms an asymmetric sliding film that compensates for the radial loads. The hydrodynamic shaft bearings 47, 48 work without contact and thus wear-free.

The plastic melt 38, which has flowed through the bearing gaps 53, 54, is fed back to the main flow H through the feed opening 45 via the discharge sections 58 and the return sections 59. The threaded shaft seals 64 promote the plastic melt 38 in the conveying direction 3, so that they generate a back pressure. The back pressure causes the plastic melt 38 on the one hand does not get to the branching gear 41 and on the other hand is passed into the return sections 59.

For temperature control of the shaft bearings 47, 48, a temperature control medium 63 is passed through the temperature control channels 62. The temperature is preferably a cooling. Cooling is necessary in particular for viscous plastic melts 38, which generate heat when flowing through the bearing gaps 53, 54. Additionally or alternatively, a temperature control 68 is passed through the temperature control 67.

The following is based on Fig. 6 A second embodiment of the invention described. In contrast to the first exemplary embodiment, the feed conveying direction 61 of the feed elements 60 is rectified relative to the conveying direction 3. The feed section 57 is formed by a respective feed channel 65 which opens into the bearing bore 50 between the threaded shaft sealing element 64 and the shaft bearing 48. Between the threaded shaft seal 64 and the shaft bearing 48, the loading element 60 is arranged on the shaft 28, which enters the plastic melt 38 entering the bearing bore 50 in the direction of loading 61 promotes to the shaft bearing 48. The discharge section 58 is arranged in the conveying direction 3 downstream of the shaft bearing 48. In the discharge section 58, a conveying element 66 is arranged on the shaft 28, which conveys the plastic melt 38, which has flowed through the bearing gap 54, into the housing bore 15 and returns the secondary flow N into the main flow H. The discharge section 58 thus simultaneously forms the return section.

The plastic melt 38 is provided with a melt pressure p and divided into a main flow H and a secondary flow N. The secondary flow N is forced through the supply channels 65 to the feed elements 60, where they promote the secondary flow N to the shaft bearings 47, 48. After flowing through the bearing gaps 53, 54, the secondary flow N is supplied to the main flow H by means of the conveying elements 66 in the housing bores 14, 15. The main flow H is guided in the usual way through the feed opening 45 in the housing bores 14, 15 and processed by means of the treatment elements 29 to 37 and 29 'to 37' in the screw machine 1 and conveyed in the conveying direction 3. With regard to the further construction of the screw machine and the further operation, reference is made to the first embodiment.

Claims (15)

Screw machine for the treatment of plastic melts, with a housing (2), at least one housing bore (14, 15) formed in the housing (2), - One in the at least one housing bore (14, 15) opening feed opening (45) for supplying a plastic melt (38), at least one treatment element shaft (16, 17), - Which in the associated housing bore (14, 15) and is rotatably driven about an associated axis of rotation (18, 19), and - Which for the treatment of the plastic melt (38) a plurality of treatment elements (29 to 37, 29 'to 37') which in a conveying direction (3) of the plastic melt (38) successively rotatably arranged on at least one associated shaft (27, 28) are, - At least one relative to the conveying direction (3) upstream of the feed opening (45) arranged shaft bearing (47, 48) for supporting the at least one shaft (27, 28) in the housing (2), characterized,
that the at least one shaft bearing (47, 48) is hydrodynamically formed. Screw machine according to claim 1, characterized
in that the at least one shaft bearing (47, 48) comprises a bearing gap (53, 54) which can be formed in particular in an annular manner. Screw machine according to claim 1 or 2, characterized
the at least one shaft bearing (47, 48) a bearing gap (53, 54) radially to the rotational axis (18, 19) has a gap width has B, wherein a ratio of the gap width B to a diameter D _W of the at least one shaft (27, 28) in the region of the at least one shaft bearing (47, 48) is: 0.0005 ≦ B / D _W ≦ 0.02, in particular 0.001 ≦ B / D _W ≦ 0.01, and in particular 0.002 ≦ B / D _W ≤ 0.005. Screw machine according to one of claims 1 to 3, characterized
in that the at least one shaft bearing (47, 48) comprises a bearing gap (53, 54) which has a gap length L in the direction of the rotation axis (18, 19), wherein for a ratio of the gap length L to a diameter D _{W of} the at least one shaft (27, 28) in the region of the at least one shaft bearing (47, 48): 0.25 ≦ L / D _W ≦ 6, in particular 0.5 ≦ L / D _W ≦ 4, and in particular 1 ≦ L / D _W ≦ second Screw machine according to one of claims 1 to 4, characterized
that the at least one shaft bearing (47, 48) a bearing gap (53, 54) which can be traversed for forming a hydrodynamic bearing from the plastic melt (38), and in particular with the at least one housing bore (14, 15) in connection , Screw machine according to one of claims 1 to 5, characterized
in that the at least one shaft bearing (47, 48) comprises a bearing gap (53, 54) which forms a partial section of a melt channel (55, 56), and
that through the melt channel (55, 56), a secondary stream (N) of the plastic melt (38) into a main flow (H) of the plastic melt (38) can be fed. Screw machine according to one of claims 1 to 6, characterized
in that the at least one shaft bearing (47, 48) comprises a bearing gap (53, 54) which forms a partial section of a melt channel (55, 56) for a secondary flow (N) of the plastic melt (38), and
in that a feed section (57) of the melt channel (55, 56) relative to the conveying direction (3) of a main flow (H) of the plastic melt (38) is arranged downstream of the bearing gap (53, 54). Screw machine according to claim 7, characterized
in that a feed element (59) is arranged in the feed section (57) which has a feed conveying direction (61) running opposite to the conveying direction (3) in order to form the secondary flow (N). Screw machine according to one of claims 1 to 7, characterized
in that the at least one shaft bearing (47, 48) comprises a bearing gap (53, 54) which forms a partial section of a melt channel (55, 56) for a secondary flow (N) of the plastic melt (38), and
that a supply portion (57) of the melt channel (55, 56) relative to the conveying direction (3) of a main flow (H) of the plastic melt (38) upstream of the bearing gap (53, 54) is arranged. Screw machine according to one of claims 1 to 9, characterized
by a starting pump (46) for supplying a lubricant, in particular the plastic melt (38), into the at least one shaft bearing (47, 48). Screw machine according to one of claims 1 to 10, characterized
that the housing (2) and / or the at least one shaft (27, 28) is (47 48) formed in the temperature-range of the at least one shaft bearing. Screw machine according to one of claims 1 to 11, characterized
in that, relative to the conveying direction (3), upstream of the at least one shaft bearing (47, 48) a sealing element (64) is arranged, which is designed in particular as a threaded shaft sealing element (64). Process for the preparation of plastic melts, comprising the following steps: - Providing a screw machine (1) with a housing (2), at least one housing bore (14, 15) formed in the housing (2), - One in the at least one housing bore (14, 15) opening feed opening (45) for supplying a plastic melt (38), at least one treatment element shaft (16, 17), --- in the associated housing bore (14, 15) arranged and about an associated axis of rotation (18, 19) is rotationally driven, and --- which for the treatment of the plastic melt (38) a plurality of treatment elements (29 to 37, 29 'to 37'), in a conveying direction (3) of the plastic melt (38) successively rotatably on at least one associated shaft (27, 28) are arranged Providing a plastic melt (38), Feeding the plastic melt (38) through the feed opening (45) into the at least one housing bore (14, 15), Preparing the plastic melt (38) by means of the at least one treatment element shaft (16, 17), wherein the at least one shaft (27, 28) during the preparation by means of at least one relative to the conveying direction (3) upstream of the feed opening (45) arranged shaft bearing ( 47, 48) is mounted hydrodynamically in the housing (2). Method according to claim 13, characterized in that
that the plastic melt (38) into a secondary stream (N) and a main stream (H) is divided,
that the secondary flow (N) flows through a bearing gap (53, 54) of the at least one shaft bearing (47, 48), and
in particular that the secondary flow (N) is supplied to the main flow (H) after flowing through the storage gap (53, 54). Method according to claim 13 or 14, characterized
that the plastic melt (38) is provided with a melt pressure p, where: 0.01 bar ≤ p ≤ 20 bar, in particular 0.1 ≤ p < 10 bar, in particular 0.5 bar ≤ p ≤ 5 bar, and in particular 1 bar ≤ p < 3 bar.

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